Electrical protection systems and methods having improved selectivity

Abstract

An electrical protection method for detecting an electrical fault in an electrical installation includes: measuring electrical variables by way of an auxiliary protection device, the electrical variables being associated with phase conductors; automatically analysing the measured electrical variables in order to identify a condition representative of a short circuit between phase conductors; detecting an electrical fault, such as a short circuit between the three electrical phases associated with the phase conductors without any neutral conductor involved, based on the measured electrical variables; triggering the opening of a switching device of the auxiliary protection device when an electrical fault is identified in order to disconnect one of the phase conductors, the switching device being connected to one of the phase conductors.

1 . An electrical protection method for detecting an electrical fault in an electrical installation, said electrical installation comprising at least one electrical source based on a switching power converter and a protection system, said electrical source being connected to the rest of the three-phase electrical installation by phase conductors, the protection system comprising at least one protection device and an auxiliary protection device associated with the electrical source, the method comprising:
 measuring electrical variables by way of the auxiliary protection device, the electrical variables being associated with the phase conductors;   automatically analyzing the measured electrical variables, by means of an electronic control device of the auxiliary protection device, in order to identify a condition representative of a short-circuit between said phase conductors;   detecting an electrical fault, such as a short-circuit between the three electrical phases associated with said phase conductors without any neutral conductor involved, based on the measured electrical variables; and   triggering the opening of a switching device of the auxiliary protection device when an electrical fault is identified by the electronic control device, in order to disconnect one of said phase conductors, said switching device being connected to one of said phase conductors between said electrical source and the rest of the electrical installation.   
     
     
         2 . The electrical protection method according to  claim 1 , wherein the electrical variables are alternating electric voltages measured on the phase conductors connecting said electrical source to the rest of the electrical installation, the measurement of said electric voltages being carried out by voltage sensors of the auxiliary protection device. 
     
     
         3 . The electrical protection method according to  claim 1 , wherein, following the opening of the switching device by way of the auxiliary protection device, the electric current circulates between said electrical source and the rest of the electrical installation in said phase conductors that have not been opened, with this current leading to the triggering of at least one of the protection devices. 
     
     
         4 . The electrical protection method according to  claim 1 , wherein automatically analyzing the measured electrical variables comprises a comparison of at least some of the measured values with a predefined reference threshold or with a reference waveform, and wherein an electrical fault such as a short-circuit between the three electrical phases is detected if the measured values are considered to be low enough and/or similar. 
     
     
         5 . The electrical protection method according to  claim 1 , wherein the protection devices are configured so as to have predefined selectivity for the scale of the electrical installation. 
     
     
         6 . An electrical protection system for an electrical installation comprising at least one electrical source based on a switching power converter, the protection system comprising at least one electrical protection device and an auxiliary protection device associated with the electrical source, the auxiliary protection device being configured for:
 measuring electrical variables by way of the auxiliary protection device, the electrical variables being associated with the phase conductors;   automatically analyzing the measured electrical variables, by means of an electronic control device of the auxiliary protection device, in order to identify a condition representative of a short-circuit between said phase conductors;   detecting an electrical fault, such as a short-circuit between the three electrical phases associated with said phase conductors, based on the measured electrical variables; and   triggering the opening of a switching device of the auxiliary protection device when an electrical fault is identified by the electronic control device, in order to disconnect one of said phase conductors, said switching device being connected to one of said phase conductors between said electrical source and the rest of the electrical installation.   
     
     
         7 . The electrical protection system according to  claim 6 , wherein the switching device comprises an electromechanical switch, or a semi-conductor switch or a hybrid switch. 
     
     
         8 . The electrical protection system according to  claims 6 , wherein the auxiliary protection device is integrated in a protection device associated with said electrical source. 
     
     
         9 . The electrical protection system according to  claim 6 , wherein the auxiliary protection device is a separate device from a protection device associated with said electrical source. 
     
     
         10 . An electrical installation comprising an electrical source based on a switching power converter and the electrical protection system according to  claim 6 .